Field
This invention relates generally to a system and method for automated coatings application in a spray booth and, more particularly, to a system and method that provides automated adaptations for an object as-built and as-located in a spray booth to determine optimal spray paths for coating the object, where the system and method also measure thicknesses of the coatings that are being applied to the object in the spray booth using integrated sensing devices and a computing subsystem such that precise coating thicknesses may be achieved with limited human interaction.
Discussion
Coatings application specifications for manufactured objects such as airplanes, vehicles, parts, etc. typically require that the thickness of the coating applied be within precise tolerances to meet the required specifications. For example, stealth coatings on military aircraft must be within a narrow range to be acceptable for use. The task of achieving the required precision in coating thicknesses is particularly challenging when the surface being coated has a complex geometry, as is typical of military aircraft and military equipment.
Coatings are usually applied using industrial robots, sometimes referred to as coatings applications robotics or robotic spray guns, followed by a lengthy process of sanding and recoating to achieve the desired precise thicknesses over the various contours of the object. For example, one or more multi-axis industrial robots, such as six-axis robots, that are capable of moving along at least x- and y-rails, and possibly a z-axis lift, are typically used to apply coatings to objects. Many factors must be considered when employing such robots that affect coating thickness, such as material flowrate, air pressure (both fan and atom), robot speed, number of coats, stepover distance, standoff distance, robot position and speed accuracy, aircraft/object position accuracy, coating delivery system accuracy, as well as booth temperature, humidity and airflow speed. This process requires a significant amount of time and manual labor to achieve the desired results.
Using known spray techniques, the object to be sprayed is located in a spray booth in a predetermined position with little room for error to ensure that the robots do not come into contact with the object being coated and to ensure that the coatings are applied to the desired thicknesses. Damaging the object being sprayed or the robot through contact between the object and the robot is extremely undesirable, particularly when, for example, an aircraft that cost over one billion dollars to manufacture is the object being coated. Additionally, inaccurate object positioning may lead to inaccurate coating thickness, requiring more sanding and/or recoating and thereby increasing the time and labor costs associated with coating the object. Thus, known systems require an object to be located in an exact position in the spray booth or require significant testing and reconfiguration to compensate for deviations in location, i.e., to compensate for the object “as-located”.
An additional problem with trying to achieve precise coating thicknesses on an object is the issue of object variation. Using the example of a stealth bomber aircraft, there may be slight variations among the stealth bombers that are manufactured, e.g., a wing tip may sag differently between one stealth bomber and the next. Thus, simply using model programs for the expected shape of an object to be sprayed may lead to imprecise coating thicknesses. The variation that may occur between the shape of the manufactured object, i.e., the as-built object, and the shape of either that object as modeled or as measured from a previous complete spray of an object that is an object of the same manufacture may lead to inaccurate coating thicknesses due to these as-built variations. Additionally, the known coatings application system requires that the object position be within the spray booth in an almost exact location, as stated above. The known coatings application system must be tested and reconfigured to account for any deviation from the expected location of the object within the spray booth as well as any as-built variations to ensure a collision between the robots and the object does not occur. This testing and reconfiguring process requires manual labor and is time consuming.
Thus, there is a need in the art for a system and process for applying coatings to objects in a spray booth that automatically takes into consideration the object as-located and as-built such that a lengthy test process is eliminated. There is further a need in the art to use the as-located and as-built measurements in combination with coating thickness measurements taken during coating of the object such that spray paths of the robots may adapt during coatings application to ensure that the object is coated within predetermined thickness requirements with minimal sanding and/or respraying.